Enhanced size-dependent trapping of particles using microvortices

Inertial microfluidics has been attracting considerable interest for size-based separation of particles and cells. The inertial forces can be manipulated by expanding the microchannel geometry, leading to formation of microvortices for selective isolation and trapping of particles or cells from a mixture. In this work, we aim to enhance our understanding of particle trapping in such microvortices by developing a model of selective particle entrapment. Design and operational parameters including flow conditions, size of the trapping region, and target particle concentration are explored to elucidate their influence on trapping behavior. Our results show that the size dependence of trapping is characterized by a threshold Reynolds number, which governs the selective entry of particles into microvortices from the main flow. We show that concentration enhancement on the order of 100,000× and isolation of targets at concentrations as low as 1/mL is possible. Ultimately, the insights gained from our systematic investigation suggest optimization solutions that enhance device performance (efficiency, size selectivity, and yield) and are applicable to selective isolation and trapping of large rare cells as well as other applications.     

Abstract stimulus-specific adaptation models

Many neurons that initially respond to a stimulus stop responding if the stimulus is presented repeatedly but recover their response if a different stimulus is presented. This phenomenon is referred to as stimulus-specific adaptation (SSA). SSA has been investigated extensively using oddball experiments, which measure the responses of a neuron to sequences of stimuli. Neurons that exhibit SSA respond less vigorously to common stimuli, and the metric typically used to quantify this difference is the SSA index (SI). This article presents the first detailed analysis of the SI metric by examining the question: How should a system (e.g., a neuron) respond to stochastic input if it is to maximize the SI of its output? Questions like this one are particularly relevant to those wishing to construct computational models of SSA. If an artificial neural network receives stimulus information at a particular rate and must respond within a fixed time, what is the highest SI one can reasonably expect? We demonstrate that the optimum, average SI is constrained by the information in the input source, the length and encoding of the memory, and the assumptions concerning how the task is decomposed.     

Influence of stimulants on electrodermal studies in Fragile X syndrome

Attention Deficit Hyperactivity Disorder (ADHD) is seen in the majority of children with Fragile X Syndrome (FraX). Previous work has documented an enhanced sweat response to stimuli in children with FraX compared to controls utilizing electrodermal response (EDR) measures. The present study assesses the EDRs both on and off stimulants in 19 children with ADHD and FraX compared to 17 age- and IQ-matched control patients with ADHD and developmental delays. Although the baseline EDRs were comparable between FraX patients and controls, the patients with FraX had a significant decrease in EDR amplitude and number of peaks when treated with stimulants compared to controls. This suggests that patients with FraX are more responsive to the enhancement of inhibitory systems that occur with stimulant use for ADHD. The use of a quantifiable measure, such as EDR, is recommended in future studies of treatment efficacy.     

Fretting wear of Ti-48Al-2Cr-2Nb

An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296–823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473–823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.     

Bachelor Culture in the Work of Adolf Loos

The issue of gender in the architecture and writing of Adolf Loos arose from an ongoing debate over gender identification and roles in Viennese culture of the fin-de-sie`cle. Loos's critique challenged what he saw as the degradation of contemporary culture through its feminization. His masculinized alternative reclaimed the public realm for the rational and the pragmatic. Through this crucial maneuver, Loos tied modernity back to its class base, to an ideology of production and progress, and brought nineteenth-century positivism forward into the twentieth century, jumping over the "effeminate" interlude of art nouveau.     

The influence of soil remediation on lead in house dust

Lead in house dust has long been recognized as a principal source of excess lead absorption among children at the Bunker Hill Superfund Site (BHSS) in northern Idaho. House dust lead concentration from homeowner's vacuum cleaner bags has been monitored since the epidemic of childhood lead poisoning in 1974. Geometric mean house dust lead concentrations decreased from >10000 mg/kg in 1974 to approximately 4000 mg/kg in 1975, in response to air pollution control initiatives at the defective primary lead smelter. After smelter closure, 1983 mean dust lead concentrations were near 3000 mg/kg and were most dependent on soil sources. Following emergency soil removals from public areas and roadsides and fugitive dust control efforts in the mid-1980s, house dust lead decreased by approximately 40-60% to 1200-1500 mg/kg. In 1992, a cleanup goal of 500 mg/kg dust lead community average, with no individual home exceeding 1000 mg/kg, was adopted. This goal was to be achieved by a combination of contaminated soil removals and fugitive dust control efforts throughout the 21 square mile BHSS. Continual reductions in house dust lead concentrations have been noted throughout the residential area soil cleanup. Geometric mean house dust lead concentrations averaged approximately 500-600 mg/kg from 1996 to 1999 and dropped below 500 mg/kg in 2000. Analysis of these data indicates that approximately 20% of the variance in dust lead concentrations is attributed to yard, neighborhood, and community soil lead concentrations. Since 1996, dust lead concentrations and dust and lead loading rates have also been measured by dust mats placed at entryways into the homes. Neighborhood soil lead concentrations, household hygiene, the number of adults living in the home, and the number of hours a child spends outdoors in summer explain approximately 26% of the variance in mat dust lead loading rates. It is estimated that post-remedial house dust lead concentrations will stabilize at 400-500 mg/kg, as compared to approximately 200 mg/kg in socio-economically similar background communities; the difference possibly attributed to residual soil concentrations (3-6 times background), recontamination of rights-of-way, tracking of non-residential mining district soils and dusts, fugitive dusts associated with the remediation, and residual structural or carpet dusts.     

Effect of medium-pressure UV irradiation on bromate concentrations in drinking water, a pilot-scale study

This study investigated the potential for bromate removal from drinking water on irradiation with medium-pressure UV lamps-a technique gaining considerable interest for drinking water disinfection. Waters from two different sources were spiked with 20microg/L of bromate and irradiated with UV fluences up to 718mJ/cm(2) utilizing a pilot-scale reactor (Calgon Carbon Corp.) at a flow of 76L/min (20 gallon/min). Essentially no removal was observed in one of the source waters. Limited bromate removal, up to 19%, was observed in the second source water at high UV fluences (696mJ/cm(2)) and a fluence-response relationship was clearly evident. All removals would be negligible at UV fluences anticipated for drinking water disinfection (< or =40mJ/cm(2)). Different water characteristics, in particular competitive absorption by nitrate and possibly DOC, were most likely responsible for the differences in bromate removal in the waters tested. The source water that did not show any removal had a higher nitrate concentration (4 vs. 0.1mg N/L) and also a higher DOC concentration (4.1 vs. 3.1mg C/L) than the other source water which showed 19% bromate removal.     

Absorption effects in photopolymerized ceramic suspensions

The effects of concentration of photoinitiator and concentration of an ultraviolet-absorbing dye on the cure depth and cure width of photopolymerized ceramic suspensions were investigated. Both the cure depth and cure width have a semilogarithmic dependence on the energy dose, with the suspension characterized by the following parameters: the depth critical energy dose and depth sensitivity and width critical energy dose and width sensitivity. The values of these four parameters are highly dependent on the concentration of absorbers in the suspension. The depth sensitivities and width sensitivities are given by the absorption model, while the depth critical energy doses and width critical energy doses are given by the inhibitor exhaustion model. Furthermore, the relationship between concentration of absorbers and the broadening depth was determined. The concentration of photoinitiator did not significantly change the broadening depth, while the concentration of dye decreased the broadening depth.     

Gelation properties of salt-extracted pea protein induced by heat treatment

Gelation is one of the most important properties of plant proteins. In this paper, a low denaturation salt extraction method was used to extract pea (Pisum sativum L.) protein isolate from commercial pea flour. The gelation properties of this isolate were examined and compared to commercial products. The pea protein isolate followed the three-step process of gelation that is generally accepted for heat-induced gelation of globular proteins. The minimum gelation concentration of salt-extracted pea protein isolate (PPIs) was 5.5% while that of commercial pea protein isolate (PPIc) was 14.5%. The gelling point was in the range of 82–86 °C for 14.5% PPIs, 0.3 M NaCl at natural pH (5.65). With increasing heating rate, the gelling point tended to increase. Higher heating and cooling rates resulted in decreased final G′ (storage modulus) and G″ (loss modulus) values, indicative of decreased gel strength. A higher protein concentration resulted in higher G′ and G″ values and it was found that there was a power law relationship between protein concentration and G′ and G″. Tan delta (δ) values decreased with increasing protein concentration and at concentrations of 5.5% and above, tan δ remained constant which means the critical concentration for gel formation was 5.5%. The values of G′ and G″ for PPIs were greater than those of PPIc, and tan δ of PPIs was smaller, indicative of a stronger gel network. DSC data showed that PPIc had undergone denaturation whereas PPIs had not (ΔH = 15.81 J/g protein). Although rheometer data showed that the final G′ value of commercial soy protein isolate (SPIc) was smaller than that of PPIs, the gel prepared with SPIc was visually stronger than that of PPIs. The rheological data obtained with small amplitude oscillatory testing was not consistent with the actual observations. Overall, the low degree of denaturation of the PPIs resulted in a stronger gel than that of PPIc making the PPIs a more attractive food ingredient.     

Fit for the task: the future of the small scale domestic repair and maintenance industry in the UK

The poor condition of much of the UK's older housing stock is an important policy issue. Some disrepair arises because owners cannot afford work, because they are not aware of the need for it or because they do not know how to go about organizing it. However, the poor reputation of that sector of the building industry dealing with small scale domestic repair and maintenance is also a deterrent. If anything, the problems of this sector have worsened during the recession as the supply of unskilled ‘cowboy’ operators has increased. This paper reviews the factors leading to underinvestment and poor quality work in the privately owned housing stock and examines the extent to which the shortcomings of the building industry contribute to this phenomenon. It describes the results of a survey of firms operating in the domestic repair and maintenance sector of the UK building industry, the majority of which were very small. The survey examined the size and composition of firms, their organization and working practices, the types of work they carried out, how they went about obtaining business, the extent to which their work-force was trained and the problems they faced in competing with one another and with the cowboy sector. On the basis of the survey conclusions and discussions with a wide range of organisations representing the industry, consumers, local authorities and government, a series of options for reform are discussed with the aim of stimulating debate on the future of this sector of the construction industry. It is argued that the problems of the UK industry cannot be solved by tighter controls on builders alone, but by a range of measures designed to provide more support and training to reputable builders, measures to exert greater controls over building techniques and safety provision to reduce unfair competition and programmes to educate the consumer to demand better standards and to be willing to pay for them. Ultimately only compulsory measures may succeed in improving standards, but much could be achieved by voluntary licensing or registration schemes backed up by incentives to use qualifying firms such as guarantees. This is more likely to work if backed up for an initial period by government or local authority funding. In the long run, however, the improvements to building quality could save public money.